A tropical wave in the western Caribbean approaching Mexico's Yucatan Peninsula is generating disorganized thunderstorms. Wind shear is a moderate 10 - 15 knots over the region, and water vapor satellite images show that there is some dry air to the west that will interfere with any development that might occur. None of the reliable computer models develop this wave, and NHC is giving it a 10% chance of developing into a tropical depression.

Figure 1. Morning satellite image of the disturbed region of weather of the coast of Africa, south of the Cape Verdes Islands.

The GFS, NOGAPS, and ECMWF models continue to predict that a tropical storm will form between Africa and the Lesser Antilles Islands sometime in the period 3 - 6 days from now. There is an area of disturbed weather south of the Cape Verdes Islands, but there is no obvious organization to the cloud pattern. Wind shear is a hefty 20 - 30 knots in the region, and the disturbance is a 1 - 2 day journey away from reaching a lower shear area where development can occur. Preliminary indications are that if a storm did develop in this region, it would track west-northwest and pass well to the northeast of the Lesser Antilles Islands 7 - 8 days from now. However, 7-day forecasts of a storm that hasn't even formed yet are not to be trusted.

Figure 2. The cold front that brought an end to the Great Russian Heat Wave of 2010 lies east of Moscow in the NASA MODIS photo taken at 8:35 UTC August 19, 2010. Smoke from wildfires is visible over a wide swath of Russia east of the front. Image credit: NASA.

The Great Russian Heat Wave of 2010 endsA powerful cold front swept through Russia yesterday and today, finally bringing an end to the Great Russian Heat Wave of 2010. Temperatures at Moscow's Domodedovo airport hit 25°C (77°F) today, which is still 4°C (7°F) above average, but the high temperature since late June. Moscow has seen 62 consecutive days with a high temperature above average, but the latest forecast for Moscow predicts that remarkable string will come to an end Friday, when the high will reach just 17°C (62°F).

Massive 926 mb extratropical storm generating huge waves off AntarcticaOne of the most intense extratropical storms in recent years is churning up the waters near the coast of Antarctica in the South Indian Ocean. The powerful storm peaked in intensity yesterday afternoon with a central pressure of 926 mb--the type of pressure typically found in a Category 4 hurricane. Storms this intense form on average once per year, or perhaps less often, according to an email I received from Jeff Callaghan of the Australia Bureau of Meteorology. Since extratropical storms do not form eyewalls, the winds at the surface from this monster storm probably reached "only" 100 - 120 mph (equivalent to a Category 2 or 3 hurricane.) The storm is forecast to generate huge waves with a significant wave height of 13 meters (44 feet) today, according to the NOAA Wavewatch III model (Figure 3.) I have flown into an extratropical storm this intense--in 1989, I participated in a field project based in Maine that intercepted a remarkable extratropical storm that "bombed" into a 928 mb low south of the Canadian Maritime provinces. You can read my story of that somewhat harrowing flight here.

Figure 3. Satellite image taken at 8:10 UTC August 19, 2010, showing the intense extratropical cyclone that has weakened to 940 mb in the South Indian Ocean near the coast of Antarctica. Image credit: NASA.

Figure 4. Surface pressure analysis from 18 UTC August 18, 2010, showing a 926 mb low in the South Indian Ocean, just north of Antarctica. Image credit: Jeff Callaghan, Australia Bureau of Meteorology.

Figure 5. Predicted wave height from the NOAA Wavewatch III model for 2pm EDT (18 UTC) today, August 19, 2010. Peak wave heights of 13 meters (44 feet) are projected over ocean areas between Antarctica and Australia. Long-period waves (19 seconds between crests) up to 7 meters (22 feet) high are predicted to affect the southwest coast of Australia by Sunday. The waves are predicted to propagate eastwards to New Zealand 8 - 9 days from now, and be a respectable 4 - 5 meters high then.

Quoting galvestonhurricane:Levi: What are your thoughts on the steering of PGI31L?

Well west at first but with the tropical wave off to the northwest and not yet having a completely developed system, it's hard to say when it will start gaining latitude. That's the key thing to watch for early on which will largely determine where it recurves.

You mean the tropical wave behind? Ya that could be a little limiting factor for PGI31L in the short-term, but it should be overwhelmed by the larger monsoonal circulation and get absorbed during the next 2 days.

That was what I was thinking too. Thought it was a nice little spin though.

Go look at Hurricane Alicia and Hurricane Rita then. Yes you heard me right, Rita in 2005 was a product of a trough-split.

Yep.

"The storm system that became Rita formed at the tail of an old frontal boundary, where convection and low-level circulation around an upper-level low developed steadily for over two days. On September 17 the National Hurricane Center concluded that it had enough tropical disturbance had acquired enough convective organization to be classified a tropical depression, and so named it Tropical Depression 18."

You mean the tropical wave behind? Ya that could be a little limiting factor for PGI31L in the short-term, but it should be overwhelmed by the larger monsoonal circulation and get absorbed during the next 2 days.

Quoting help4u:Trough splits never develop into much just lots of rain,no wind and i thought this season was going to be a high impact on the United States ,seems like every storm is forcast to miss by several hundred miles.

Go look at Hurricane Alicia and Hurricane Rita then. Yes you heard me right, Rita in 2005 was a product of a trough-split.

Trough splits never develop into much just lots of rain,no wind and i thought this season was going to be a high impact on the United States ,seems like every storm is forcast to miss by several hundred miles.

Quoting Abacosurf: Seems like the conditions for low pressure in the gulf may persist for some time. Most likely until there is a release

Seems like an early october type pattern...

Seems like a La Nina pattern. An October pattern are the kind of huge troughs that can recurve hurricanes up out of the Caribbean. We are not seeing such troughs. La Nina is what causes all the trough-splitting in seasons like this, which can add a handful of storms to the season total in addition to the ones that originate in the deep tropics.

note am not talking about 09 am talking about jason2010xxxx the one is driveing me nuts and i even have jason2010xxxx on Ignore so i did not want too think i was talking too 09 and takeing this the worng way

Quoting Levi32:I think it's pretty obvious we have a rapidly developing monsoonal depression SSW of the Cape Verde Islands. This should be a tropical depression or storm within the next 48 hours.

Where it recurves will be determined largely by how far west it moves before starting to gain latitude. This will be one of those storms that, if it passes north of 20N before hitting 60W, will likely recurve. Model runs have shifted back north and the developing pattern looks to be letting a trough slip down under the ridging, so a recurve east of the United States is a good bet at this point, but until the system is solidly formed watch the track over the next 5 days to see if things change.

Homegrown mischief may also be a problem yet again in 3-4 days as another trough-split occurs over the Gulf of Mexico.

GFS 108 hours 500mb shows the split:

Seems like the conditions for low pressure in the gulf may persist for some time. Most likely until there is a release